$50 Facebook Marketplace CB350 in boxes

Kags1969

New Member
I am an older guy (born 1969) and I found a 1972 CB350 on FB marketplace. It came with a title (which I just transferred) The young man (mid-late 30's) had purchased a running cb350 and wanted to learn on it, so he took it apart and had the case bead blasted, but other projects took priority and I think it just started gathering dust. He bagged and labeled everything, but the engine is completely disassembled. I got three tubs of parts. I want to put it back together, but have never split a case. Done top ends, and lots of other mechanical work, but never put one together from scratch. There are a couple of issues that I see off the bat and wanted to ask about ( and I will search).

1.) There is a snapped off valve guide, broken at the head. - What is the best method to extract for a home mechanic or does this need to go to a machinist?
2.) There are two bolt through holes on the lower case, one has about half of the circle snapped off. Should I source a new lower case or just work with the imperfect and is it super critical. If so can it be tig welded back to health (is it worth it if I have to pay someone to do?)

This was really priced as a gift to give another enthusiast a chance to get the bike back on the road.
 

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So the first problem I want to solve is the valve guide problem. Let me describe it a little better as I am not sure about the components after looking up valve guide parts for the CB at common motore. The spring seat snapped off from what I am calling the valve guide at the head, so the spring seat in no longer attached to the head and the "valve guide" remained in the head. I need to determine all the pieces that make that set of components up and determine next step. If I have to replace that I would like some machinist recommendations for CB work. I am assuming I would just replace the broken valve guide and valve seat and have the seat cut to either a new valve or the old valve. I will get some pics up as a picture is worth a 1000 words. Edit - added a couple of pics
 

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You can DIY the guide but it's going to need reaming to size after fitting plus valve seat will need to be cut.
You use a piloted drift, slightly under diameter of guide with pilot same diameter as valve stem.
The spring seat actually slides over top of guide
Unless shop is familiar with motorcycles and old Honda's in particular, it may be difficult for them to actually do.
It's normal to heat head around 250f to remove or re-fit guides.
Putting them in too deep can make the stop ring (an external wire circlip) squeeze guide which may crack same as what you already have (I've seen it happen direct from factory, burning oil, on stripping top end, top of guide broken off).
There are special tools available but personally I've only ever seen pictures of them as Honda would prefer to fit a new head under warranty and majority of 'old' bikes' ended up scrapped after 5~10 years when repairs got this expensive (honestly, I've only ever done one complete valve guide replacement at a dealers, Suzuki GS850 as owner liked it and wanted to keep it)
 
You can DIY the guide but it's going to need reaming to size after fitting plus valve seat will need to be cut.
You use a piloted drift, slightly under diameter of guide with pilot same diameter as valve stem.
The spring seat actually slides over top of guide
Unless shop is familiar with motorcycles and old Honda's in particular, it may be difficult for them to actually do.
It's normal to heat head around 250f to remove or re-fit guides.
Putting them in too deep can make the stop ring (an external wire circlip) squeeze guide which may crack same as what you already have (I've seen it happen direct from factory, burning oil, on stripping top end, top of guide broken off).
There are special tools available but personally I've only ever seen pictures of them as Honda would prefer to fit a new head under warranty and majority of 'old' bikes' ended up scrapped after 5~10 years when repairs got this expensive (honestly, I've only ever done one complete valve guide replacement at a dealers, Suzuki GS850 as owner liked it and wanted to keep it)\
Thank you for the reply. I have lots of questions.

1.) The valve guide broke, if I replace the valve guide, do I have to replace the valve and the seat? Can I reuse the old valve ( I don't think the engine was work or smoking).

2.) is there a specialty reaming tool that you use to match the size of the valve guide to the valve that you use? This seems like a machine shop type process

3.) I'm familiar with heat / cold to install bearings, seems like the same principle.
 
No need to replace the seats. Your old valves should be OK as long as they are in spec and aren't bent. Get good valve seals.

hard to tell in the photos, but if looks like you valve seats might have some cupping - check your valves as well. If thats the case I would pass it off to a machine shop to handle cutting new valve seats, grinding the valves, and installing a new guide. They will also be able to check it for flatness to see if you need it decked. There are lots of places to skimp in a project like this but the head is not one where I personally cut corners - it usually ends up as false economy. This is stuff that most local shops can do no problem. If you are willing to ship I have been using Shumann Motorwerks out of Milwaukie OR. He has great prices and specializes in vintage Japanese stuff.
 
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I don't have any recs for Austin, but when I lived in Houston Harold's Automotive Machine Shop in Richmond TX did a top notch job on the top end of my BMW. For a $50 bike it would be worth shelling out the cash to have the valves and seats done correctly.
 
True. For a $50 bike it might even be worth your while to find another head. Lots of them out there; eBay and other sources.
 
See if you can find a motorcycle salvage yard or salvage warehouse. They usually aren't too publicized but if you can find one within driving distance it's like finding a gold mine. Someone on here might have a spare 350 head also, worth a try; Lot's of good people on here.
 
Here is Schumann listing for the head work. I didn't realize these CB350 heads did not use valve seals. he makes new valve guides to use valve seals. Might be a nice upgrade. If you contact him outside ebay you might get a better deal because your head is already blasted. Be wary of buying used heads, seems like most of the time they need the same work done.

 
See if you can find a motorcycle salvage yard or salvage warehouse. They usually aren't too publicized but if you can find one within driving distance it's like finding a gold mine. Someone on here might have a spare 350 head also, worth a try; Lot's of good people on here.
Thank you. I will check around here. I just found a used TL125 for a different project that I am going to try to get running in a CL100.
 
Here is Schumann listing for the head work. I didn't realize these CB350 heads did not use valve seals. he makes new valve guides to use valve seals. Might be a nice upgrade. If you contact him outside ebay you might get a better deal because your head is already blasted. Be wary of buying used heads, seems like most of the time they need the same work done.

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Thank you. I've talked to a local guy and going to stop by his shop on Saturday to look at the head and talk through the options. I appreciate the recommendation.
 
Call the guys at AF1 racing in Austin and ask who does their head work. The head has to be heated and drive the old guide out. Then a new guide has to be fitted. It may or may not need reaming to size, then all the valve seats and valves need to be cut.
 
You almost always have to ream the guides. They're not hard to ream yourself. The reamers are tapered to the length of the guide, so there's really no way of getting things off center. Same goes for cutting the seats. The good tool kits are expensive, but if you do enough heads it's worth the price. You'll spend the same to a machine shop as you would for the kit.
 
Irk, I ordered a reamer and a guide and might take a stab at it myself. I need to do a little research on the valve seats and how that are replaced just so I understand what I am dealing with. I like to think of the money I spend on this stuff as "Tuition" LOL. I have seen the seat cutters, but not sure I understand how the seats are mated to the head.
 
You can DIY the guide but it's going to need reaming to size after fitting plus valve seat will need to be cut.
You use a piloted drift, slightly under diameter of guide with pilot same diameter as valve stem.
The spring seat actually slides over top of guide
Unless shop is familiar with motorcycles and old Honda's in particular, it may be difficult for them to actually do.
It's normal to heat head around 250f to remove or re-fit guides.
Putting them in too deep can make the stop ring (an external wire circlip) squeeze guide which may crack same as what you already have (I've seen it happen direct from factory, burning oil, on stripping top end, top of guide broken off).
There are special tools available but personally I've only ever seen pictures of them as Honda would prefer to fit a new head under warranty and majority of 'old' bikes' ended up scrapped after 5~10 years when repairs got this expensive (honestly, I've only ever done one complete valve guide replacement at a dealers, Suzuki GS850 as owner liked it and wanted to keep it)
Crazy, This post makes more and more sense the more I learn and read. I saw a video on youtube where I guy threaded the insert then put a bolt in it to extract it. I am looking at heads on ebay and there are a few decent looking ones, but you never know if you are just buying a different problem.
 
I went to a title place and got the title put into my name! The taxes/fees were more than the purchase of the parts/bike.

There is a well reviewed classic bike shop here in Austin named Limey Bikes. Chis is a British man in Texas. I stopped by his shop on Saturday and we had a visit about my current state of affairs.

1.) I left with him the cylinders to order pistons and get a .5 overbore at his machinist. I also left the head with the broken valve guide to see what his machinist thinks about that. The head is otherwise very nice so will be useful to me or someone else down the line.

2.) I ordered a cleanish looking head off of ebay should the other one turn into a bunch of money to fix. Yet to arrive.

3.) I ordered a new lower case $85, the issue on this case is that the baffle tray has rust damage, so I drilled that out and will need to add some 6mm screw holes to attach the tray from the original lower case.

4.) I found a CL350 that is in pretty rough shape and bought it cause I'm a little slow.

I need some well regarded frame / component paint. I have always been a rustoleum guy for black parts. I am thinking sand down the rusty bits, por 15 that then a nice coat of paint on the entire frame for consistency. I am looking for well regarded proven products, not afraid of brush on stuff. I don't have a paint booth and dont seen that happening with my space constraints.

Thanks,
Chris
 

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